[cfe-dev] [llvm-dev] clang error: static_assert failed "Cache the hash code or make functors involved in hash code and bucket index computation default constructible"

[Brian Cain via cfe-dev]

Is it related to this libstdc++ bug?

 

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56278

 

Does your libstdc++'s hashtable_policy.h have this change?

 

https://gcc.gnu.org/viewcvs/gcc/trunk/libstdc%2B%2B-v3/include/bits/hashtabl
e_policy.h?r1=195935
<https://gcc.gnu.org/viewcvs/gcc/trunk/libstdc%2B%2B-v3/include/bits/hashtab
le_policy.h?r1=195935&r2=195934&pathrev=195935> &r2=195934&pathrev=195935

 

FWIW this test case works on clang 3.6 and 3.9.0 with the libstdc++ at
Godbolt https://godbolt.org/g/beq77a

 

-Brian

 

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Nema,
Ashutosh via llvm-dev
Sent: Thursday, December 1, 2016 12:19 AM
To: llvm-dev <llvm-dev at lists.llvm.org>; cfe-dev at lists.llvm.org
Subject: [llvm-dev] clang error: static_assert failed "Cache the hash code
or make functors involved in hash code and bucket index computation default
constructible"

 

Hi,

 

Consider below test case:

 

     1  #include <unordered_map>

     2

     3  using key=const int;

     4  struct Myhash {

     5          Myhash() = default;

     6          std::hash<int> hash_int_t;

     7          inline size_t operator()(const key& x) const throw() {

     8                  return hash_int_t(x);

     9          }

    10  };

    11  std::unordered_map<key,int, Myhash> mm;

 

It compile with gcc (version 4.8.4) whereas I'm unable to compile same with
clang.

 

Clang fails with below errors:

 

$ clang++ fail.cpp -std=c++11 -O0 -c

In file included from fail.cpp:1:

In file included from
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/unordered_map:
47:

/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/hashtable
.h:268:7: error: static_assert failed "Cache the hash code or make functors
involved in hash code and bucket index computation default constructible"

      static_assert(__if_hash_not_cached<

      ^             ~~~~~~~~~~~~~~~~~~~~~

/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/unordered
_map.h:120:36: error: member 'iterator' found in multiple base classes of
different types

      typedef typename _Hashtable::iterator             iterator;

                                   ^

In file included from fail.cpp:1:

In file included from
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/unordered_map:
48:

/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/unordered
_map.h:121:36: error: member 'const_iterator' found in multiple base classes
of different types

      typedef typename _Hashtable::const_iterator       const_iterator;

 

In file included from fail.cpp:1:

In file included from
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/unordered_map:
48:

/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/unordered
_map.h:124:36: error: member 'size_type' found in multiple base classes of
different types

      typedef typename _Hashtable::size_type            size_type;

                                   ^

 

In file included from fail.cpp:1:

In file included from
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/unordered_map:
48:

/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/unordered
_map.h:452:7: error: multiple overloads of 'erase' instantiate to the same
signature 'iterator (iterator)' (aka 'int (int)')

      erase(iterator __it)

      ^

 

Is this a known issue, or something I missed here ?

 

Regards,

Ashutosh

 

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